1. Field of the Invention
This invention relates to a hydraulically damping elastic bearings, in particular engine mounts for motor vehicles, with two rigid end walls opposite one another in the axial direction and at least two chambers containing damping fluid located axially one behind the other, whereby the chambers are connected with one another by means of a passage running in an annular fashion in an essentially radial plane and contained in a rigid component, and the intake and discharge ports each open into a chamber.
2. Description of the Prior Art
Such elastic bearings are used to mount drive units in motor vehicles of all types. In mounting internal combustion motors in motor vehicles, it is necessary on the one hand to have the softest possible suspension in order to prevent the transmission of noise, with a low self-damping which nevertheless allow the motor movements excited by the roadway to become very large and to decay almost undamped. On the other hand, large motor movements can be reduced by stiff suspensions or separate "Stuker" dampers, but that again leads to significant noise transmission to the body.
The prior art includes elastic bearings of this type (e.g. DE-OS No. 30 19 337), in which the desired damping action and the isolation action achieved can be optimized independently of one another, and where both a good damping characteristic is present, as well as a good isolation action. In theory, there is a passage which runs at a distance around the bearing axis. The principle of this passage is based on the fact that the damping action does not depend on throttling in the conventional sense with a conversion of the impact energy which occurs into thermal energy, but on the inertia of the quantity of fluid displaced in the annular passage. The annular passage is thereby housed in a rigid component, and the length of the passage is determined by the geometric conditions. A disadvantage is that the length of the passage can only be changed by changing the construction of the rigid component.
The prior art also includes engine mounts (e.g. DE-PS No. 32 46 587), which corresponds to U.S. Pat. No. 4,697,794, in which the annular throttle passage is housed in a rigid component, which is suspended elastically as a whole, and thus divides the chambers. The passage in this engine mount also has a fixed and specified length.
The above-mentioned patents are incorporated herein by reference as if the entire contents thereof were fully set forth herein.
U.S. Pat. Nos. 4,645,189, 4,660,813 and 4,697,793 are also incorporated herein by reference as if the entire contents thereof were fully set forth herein.